Brush and slip ring assembly



p 1963 H. J. c. ETHERINGTON 3,104,143

BRUSH AND SLIP RING ASSEMBLY Filed Jan. 3, 1961 INVENTOR. HARRY JAMES CHARLES ETHER/NGTON A TTO/PNEY United States Patent I 3,104,143 BRUSH AND SLIP RING ASSEMBLY Harry James Charles Etherington, Sunbury-on-Thames,

England, assignor to The Sperry Gyroscope Company Limited, Brentford, Middlesex, England, a company of Great Britain Filed Jan. 3, 1961, Ser. No. 80,074 1 Claim. (Cl. 339-5) This invention relates to slip ring arrangements for conducting electricity between portions of circuits carried on two relatively rotatable members. In such arrangements it is important that every slip ring should be accurately in register with the brush or brushes engaging it, since a small error in the positioning of the brush axially of the slip ring may increase the resistance of the sliding contact between the ring and the brush. A larger error may open the circuit or cause the brush to make contact with an adjacent slip ring. It is an object of the invention to enable a brush to be positioned and maintained precisely in register with a slip ring in the axial direction by means which does not depend upon the relative positions of the members or upon the accurate positioning of the slip ring and brush in relation to the respective members.

According to one aspect of the invention, a slip ring arrangement for conducting electricity between circuit portions carried on two relatively rotatable members includes a shaft which constitutes orturns with one of the relatively rotatable members, a slip ring secured co-axially to the shaft, a brush of conductive material engaging the slip ring, means associated with the other one of the relatively rotatable members for preventing rotation of the brush about the shaft axis with reference to the said other one of the relatively rotatable members, and means secured to the shaft for engaging the brush and maintaining the brush in register with the slip ring in the axial direction. The means associated with the slip ring may comprise a pair of flanges or discs of insulating material spaced axially and on opposite sides of the slip ring and projecting radially beyond the periphery of the slip ring whereby the brush is embraced by them.

In a preferred embodiment the slip ring arrangement has a series of axially spaced slip rings secured co-axially to the shaft, a series of flanges or discs of insulating mate rial arranged co-axially and in alternation with the slip rings so that every slip ring lies between a pair of flanges, and a brush engaging each slip ring, the flanges extending radially beyond the peripheries of the slip rings whereby the brushes are embraced by them. In one construction each slip ring is engaged by a pair of brushes on diametrically opposite sides of the ring and resilient means is provided for urging the brushes towards each other whereby they are urged against the slip ring interposed between them.

Preferably the brush pairs provide a circumferential groove or channel and the resilient means comprises a coil spring joined at its ends to form a torus and sprung into the groove, separate means being provided for the brushes on opposite sides of the ring for preventing rotation of the brushes about the shaft axis with reference to the other one of the relatively rotatable members. Conveniently this separate means comprises a pair of rods parallel with the shaft axis and fixed in relation to the other one of the relatively rotatable members, the rods passing through suitable apertures in the respective brushes of each pair. The slip rings and discs may be secured, together as a unit and the unit with the brushes and springs assembled upon it may be removable from the shaft and rods by releasing the unit from the shaft and sliding the assembly of the unit, brushes and springs longitudinally of the shaft and rods.

3,ldi,li3 Patented Sept. 17, E963 According to another aspect the invention is concerned particularly with apparatus having slip ring arrangements in which the slip rings and the brushes which engage them undergo a range of relative angular movement which can be limited for long periods. Apparatus carried on ships and having slip rings and brushes the relative angular position of which is dependent on the ships heading may be mentioned as an example.

Thus, a gyro compass may have a slip ring arrangement for passing current between the main frame of the compass, which has an orientation corresponding to the heading of the ship, and a phantom element, or direction defining element, which has an orientation corresponding to the direction of the true north. A ship that normally keeps on the same run, such as one on the transatlantic service, may be maintained for long periods on one of two fixed operational headings apart, or perhaps sequentially on a larger but still small number of operational headings. Each such heading is maintained on the average for a long period, though the ship will yaw through an angle of a few degrees about the mean heading that it is maintaining. It follows that the compass operates nearly all the time with the phantom element undergoing no more than small oscillations about one or another of a few predominant angular positions with respect to the main frame of the compass.

Under such conditions of use, the surfaces of those portions of the slip ring that are not continuously wiped by the relative motion of the brushes during yaw oscillations of the ship, tend to become tarnished due to the action of moisture, salt, dirt and oxygen and other gases in the atmosphere. There is therefore a risk that on the occasions when the ship is turned for a short time to some ending other than its principal operational headings, the brushes may not make good electrical contact with the slip rings.

According to this aspect the invention comprises apparatus provided with a slip ring arrangement including an electrically conducting slip ring engaged by a plurality of brushes at least one of which serves to convey current to or from the slip ring and of such character that the slip ring and the brushes engaging it undergo relative angular movements which can be limited in range for long periods of use by reason of conditions of operation but Which exceed a small predetermined value at frequent intervals whenever the apparatus is in use, wherein the brushes are so constructed and disposed that they make mechanical contact with the ring over contact areas of such number and extent and so disposed in relation to each other that every arcuate gap between adjacent contact arc ends is of less arcua-te length than the said pre determined value of angular movement whereby the surface of each portion of the slip ring that lies at any time between two adjacent contact arcs is frequently traversed by the adjacent brush parts. Since all parts of the slip ring periphery are frequently traversed by one or both brushes, the risk of bad electrical contact due to contamination of the slip ring surface is minimised.

In order that the invention may be more clearly understood .and readily carried into practice, .a slip ring arrangement tor use in a ships gyro compass and embodying the invention will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 shows an elevation, partly in section, of the slip ring arrangement,

FIGURE 2 shows an end view of a pair of brushes and a retaining spring which form part of the embodiment shown in FIGURE 1, and

FIGURE 3 shows a gyro-compass provided with the slip-ring arrangement of FIGURES 1 and 2.

Referring now to FIGURE 1, the slip ring arrangea men-t includes a roughly cylindrical unit l. mounted on a shaft 2, the portion of the shaft which lies within the unit being splined. The shaft 2 is rotatablyymounted in a frame 3 which constitutes a part of a gyro compass which is fixed in relation to the ship, and the shaft 2 is rotated in synchronism with a direction-defining element of the compass. The unit ll carries six metallic slip rings 4 which are engaged by six pairs of brushes 5 of which five pair only are shown in FIGURE 1.

Suitable means not shown, such as :a set screw, is provided for maintaining the unit 1 longitudinally located on the splined shaft 2 and flexible leads do from the respective slip rings are plaited into a flexible cable 6 to convey currents to circuit parts carried by the directiondefining element.

The unit 1 is constructed, except for the slip rings and the conductors connected to them, of suitable insulating material built up or moulded in a known manner, and it provides seven discs or flanges 8 which are arranged in alteration with the slip rings and extend radially beyond them, so that each slip ring lies at the bottom of a channel formed by the flange on each side.

Of the six pairs of wipers 5 engaging the slip rings, five are shown in FIGURE 1, and an end View of the remaining pair, together with a retaining spring 9, is shown in FIGURE 2. In FIGURE 1 the upper brush of each pair is shown in section, while the retaining spring is omitted from the pair of brushes nearest to the right so that their shape can more readily be seen. Each brush is formed from silver-carbon and has an inner periphery it) conforming in section to a circular arc of not quite 180". This inner periphery is of cylindrical shape and mates with the correspondingly shaped cylindrical surface of the slip ring. The brush has an outer periphery lll conforming to an arc of a circle co-axial with the circular arc defining the inner periphery. The outer periphery is channeled to receive the spring 9 :as can best be seen by examining the pair of brushes nearest to the right in FIGURE 1. Flat parallel faces 12 and 13 extend between the inner and outer peripheries. The

spacing between the faces 12 and 13 is such as to provide a working fit between the flanges 8 and the respective faces 12 and 13 when the brush is assembled to the unit 1. Each brush is pierced by an aperture 14.

Secured to the frame 3 are two rods 15 which are conveniently of metal provided with tubular covers of insulating material. These rods are of suitable diameter to pass through apertures 14 with a fair amount of clearance. The spring 9 is formed from a coil spring with a hook at each end, which hooks are engaged to provide the equivalent of a toroidal spring.

Now in assembling the slip ring arrangement, the brushes 5 and springs 9 are assembled on the unit 1 when the latter is off the shaft 2. This is done simply by taking one pair of brushes at a time, inserting their inner peripheries between the appropriate pair of flanges 8 to engage the correct slip ring, and then. placing the spring 9 in thte channeled outer peripheries of the brushes. One brush of each pair has secured to it a flexible conduotor 9a for connection to one of a series of terminals (not shown) which are carried by the frame 3. The springs 9 provide an electrical connection between the brushes of each pair.

When all the brushes and springs are assembled on the slip ring unit 1 the brushes are turn-ed about the unit to bring the brushes carrying the conductors to an appropriate side and the apertures it into alignment. Then the unit l is pushed endways on to the splined shaft 2, Y

and the apertures M- are simultaneously passed over the rods 15. The unit 1 is secured to the shaft by the set screw or other means (not shown) and the flexible conductors are connected to the terminal on frame 3.

It will be seen that the brushes are located axially by flanges E; to maintain them in register with the appropriate slip rings, while their radial positions are determined by the engagement of the slip rings with the inner peripheries of the brushes. The rods 15 play no part in locating the brushes axially and merely prevent the brushes from being carried around with the slipri-n-gs when the shaft 2 and unit 1 rotate with reference to the frame 3.

When the gyro compass is being used to steer the ship on a steady course, it is impossible to avoid small and frequent heading deviations of a :few degrees, and those deviations result in corresponding relative angular movements between the slip rings and their brushes. In designing the slip ring arrangement, the arcuate gap between the adjacent ends of pairs of brushes is made less than a value of relative angular movement between the slip rings and brushes which is frequently exceeded. In this way the whole circumference of each slip ring is kept clean even when the ship is on a particular heading for long periods.

Reference may now be had to FIGURE 3, which is a simplified drawing of a ships gyro compass provided with a slip ring arrangement as described with reference to FIGURES 1 and 2. f

The gyro-compass includes a rotor (not shown) contained with a casing 20. Casing 20 is pivoted about an axis 21 to a vertical ring 22. Axis 21 is perpendicular to the axis 23 of the rotor and is normally substantially vertical. A torsion-wire suspension contained within tube 24 supports the weight of the rotor and itscasing from the vertical ring.

Vertical ring 22 is pivoted to a phantom element 25 about an axis 26' which is horizontal when the ship is level, and phantom element 25 is pivoted about a normally vertical axis to frame 3 by a bearing conventionally shown at 27. Frame 3 is mounted in a binnacle in wellknown manners.

A mercury ballistic system, constructed and arranged to operate in a known manner but not shown, is arranged to apply torques to the rotor casing 20' which have the effect of maintaining the axis 23 of the rotor approximately in the plane of the meridian and horizontal.

Phantom element 25 is arranged to be rotated with reference to the ship so that it is maintained as nearly as the attitude of the ship permits in a predetermined angular relation with the rotor axis. To this end, the gyroscope is provided with an E-type pick-off 28 which is sensitive to small angular displacements of the rotor casing with respect to the vertical ring, and a motor29. This motor turns the phantom element appropriately in response to the pick-olf output by rotating a pinion 30 meshing with a large gear 31 at the top of the phantom element.

The rotor is electrically driven from a power source which is of course fixed with reference to frame 3., Further, the pick-off 28 has to be energised from a fixed source and its output has to be brought back to frame 3 in order to control the motor 29 from it. Thus a plurality of electrically conductive paths have to be provided between, among other components, the frame 3 and the phantom element 25. To this end a slip ring arrangement 32 is provided, constructed and arranged as described with reference to FIGURES 1 and 2. The shaft 2 of the device is geared to the large gear 31 by a train of toothed wheels 32, 33, 34 and 35 and rotates at the same rate with reference to frame 3, as the phantorn element, but in the opposite sense.

The conductors 9a soldered to the brushes of the slip ring arrangement are connected to terminals provided by a terminal box 36 carried on frame 3, and the flexible cable 6, at its end remote from the slip ring arrangement, is secured to the lower portion 37 'of the phantom element. A flexible protective covering 612 (FIGURE 1) of helical construction, made from plastic in a known manner, serves to prevent the formation of kinks in the cable. Since it is very lightly stressed, portion 37 can be very light in weight and may be constructed of sheet meta a amazes Conductive paths between the phantom element and the vertical ring and rotor casing are not shown and are provided in a known manner. Similarly the conductors carried by frame 3 and connected to conductors 9a at terminal box 36 are not shown.

The shaft 2 on which the portion 1 of the slip-ring arrangement is mounted has a second function in that it drives a signal generating device 38 responsive to the angular position of shaft 2 and hence to the heading of the ship as sensed by the gyro compass.

What is claimed is:

A slip ring and brush arrangement for conducting electricity between circuit portions carried on two relatively rotatable members, one of which is a shaft having a longitudinal axis, comprising,

(a) a plurality of slip rings axially-spaced along the longitudinal axis of said shaft and secured thereto,

(b) axially-spaced flanges of non-conductive material disposed on opposite sides of each slip ring and secured to said shaft,

(c) at least a pair of brushes of conductive material engaging each of said slip rings,

(d) each of said brushes of a pair thereof being disposed on diametrically opposite sides of respective slip rings said brushes extending radially beyond the periphery of said flanges and being provided with aligned apertures in the portions beyond the peripheries of the flanges,

(e) rods having one end secured to the other of said members and extending through said aligned apertures in said brushes to prevent rotation of the brushes about said shaft whereby said slip ring and brush arrangement may be slid on to the shaft member with said aligned apertures penetrated by said rods secured to said other member and extending parallel to the axis of said shaft for preventing rotation of said brushes,

(f) said flanges projecting radially beyond the periphery of said respective slip rings in order that the respective brushes are embraced therebetween and thus confined in their axial displacement,

(g) each of said brushes having a circumferential groove whereby the groove of a pair of brushes substantially defines a circle,

(h) resilient means surrounding the periphery of each pair of brushes and disposed in respective grooves for resiliently maintaining said brushes in engagement with respective slip rings interposed between them and,

(1) each of said brushes of a pair thereof having an arcuate contact surface substantially but not quite extending for one-half the circumference of the slip ring thereby forming an arcuate gap between adjacent contact ends of the brushes of said pair that is small compared with said arcuate surface.

References Qited in the file of this patent UNITED STATES PATENTS 2,203,806 Wolf June 11, 1940 2,473,526 Hood et al June 21, 1949 2,509,931 Krantz May 30, 1950 2,523,081 Wendt Sept. 19, 1950 2,529,634 Sciaky Nov. 14, 1950 2,581,266 Lurn Jan. 1, 1952 2,677,777 West May 4, 1954 2,759,145 Manley Aug. 14, 1956 2,931,999 Lemmerman Apr. 5, 1960 FOREIGN PATENTS 599,058 Great Britain Mar. 3, 1948 

